Biochemical Identification of Vitamin B12 Deficiency in a Medical Office
| Autor: | Franz Paul Armbruster, Joachim Schwarz, Andreas Dura, Karl Florian Wintgens, Katarina Hartmann, Thomas Dschietzig, Eduard Morstadt |
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| Rok vydání: | 2015 |
| Předmět: |
Male
medicine.medical_specialty Pathology Homocysteine Office Visits Methylmalonic acid Likelihood ratios in diagnostic testing Gastroenterology General Biochemistry Genetics and Molecular Biology chemistry.chemical_compound Predictive Value of Tests Internal medicine Ambulatory Care polycyclic compounds Humans Medicine Cutoff Vitamin B12 Immunoassay Transcobalamins medicine.diagnostic_test business.industry nutritional and metabolic diseases Vitamin B 12 Deficiency Gold standard (test) Middle Aged Vitamin B 12 Cross-Sectional Studies Early Diagnosis ROC Curve chemistry Area Under Curve Predictive value of tests Luminescent Measurements business Biomarkers Methylmalonic Acid |
| Zdroj: | Clinical Laboratory. 61 |
| ISSN: | 1433-6510 |
| DOI: | 10.7754/clin.lab.2014.141219 |
| Popis: | Background A vitamin B12 deficiency can be an underlying cause or a deteriorating factor in several diseases. Nevertheless, early identification of such a deficiency remains a problem. Holotranscobalamin (HTC) is presently considered to be the gold standard. We tested the predictive power of other B12 parameters by comparing them with HTC. Methods The blood of 77 patients from a medical office was tested for HTC, total B12 (CLIA [chemiluminescent immunoassay] and MTP [microbiological test with microtitre plates]), MMA (methylmalonic acid), HCY (homocysteine), and MCV (mean cell volume). The parameters were correlated and sensitivity, specificity, PPV (positive predictive value), NPV (negative predictive value), LR+ (positive likelihood ratio), and LR- (negative likelihood ratio) in comparison to HTC were determined. A ROC analysis was also performed. Results At a cutoff value of 35 pmol/L for HTC, the total B12 CLIA (cutoff 211 ng/L) qualified 53% of individuals as having a B12 deficiency. The total B12 MTP (cutoff 288 ng/L) classified 71% as having a B12 deficiency. Specificity was similar in both cases (CLIA, 93%; MTP, 95%). With a cutoff value of 10 µmol/L for homocysteine, the best negative prediction was achieved. MVA has a low sensitivity (41%) and a high specificity (90%). Based on the ROC analysis, which indicated superiority of the B12-MTP, the reference levels of B12-CLIA and B12-MTP were raised to 304 and 368 ng/L, respectively. Thus, a probable B12 deficiency was identified in 94% of cases with either method and with a comparable specificity. Conclusions If total B12 is applied to identify B12 deficiency, the cutoff values should be elevated to 304 (B12-CLIA) and 368 ng/L (B12-MTP) to improve the predictive power. The negative-predictive power of HCY can be useful in daily routine. HTC has a broad grey area of uncertainty and MMA should only be applied as a confirmatory test. |
| Databáze: | OpenAIRE |
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